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Title: Lanthanide(III) nitrobenzenesulfonates as new nitration catalysts: The role of the metal and of the counterion in the catalytic efficiency
Authors: Parac-Vogt, Tatjana
Pachini, Sophia
Nockemann, Peter
Van Hecke, Kristof
Van Meervelt, Luc
Binnemans, Koen # ×
Issue Date: 2004
Publisher: Wiley-v c h verlag gmbh
Series Title: European journal of organic chemistry issue:22 pages:4560-4566
Abstract: Lanthanide(III) complexes of p-nitrobenzenesulfonic acid, Ln(p-NBSA)3, m-nitrobenzenesulfonic acid, Ln(m-NBSA)3, and 2,4-nitrobenzenesulfonic acid, Ln(2,4-NBSA)3, were prepared, characterized and examined as catalyst for the nitration of benzene, toluene, xylenes, naphthalene, bromobenzene and chlorobenzene. The initial screening of the catalysts showed that lanthanum(III) complexes were more effective than the corresponding ytterbium(III) complexes, and that catalysts containing the bulky 2,4-NBSA ligand were less effective than the catalyst containing p-NBSA (nosylate) or m-NBSA ligands. Examination of a series of Ln(p-NBSA)(3) and Ln(m-NBSA)3 catalysts revealed that there is a clear correlation between the ionic radii of the lanthanide(III) ions and the yields of nitration, with the lighter lanthanides being more effective. The X-ray single crystal structure of Yb(m-NBSA)3.6H(2)O shows that two m-NBSA ligands are directly bound to the metal centre while the third ligand is not located in the first coordination sphere, but it is hydrogen bonded to one of the water molecules which is coordinated to ytterbium(III). NMR studies suggest that this structure is preserved under the conditions used in the nitration reaction. The structure of Yb(m-NBSA)3 is markedly different from the structure of the well-known ytterbium(III) triflate catalyst. The coordination of the nitrobenzenesulfonate counterion to the lanthanide(III) ion suggests that steric effects might play an important role in determining the efficiency of these novel nitration catalysts.
ISSN: 1434-193X
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Design and Synthesis
Molecular Imaging and Photonics
Biochemistry, Molecular and Structural Biology Section
× corresponding author
# (joint) last author

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